1. Field of the Invention:
This invention relates generally to pen type plotting apparatus, and more particularly to a type thereof including means for reprinting an initial part of printed patterns and the like in an overlying manner for avoiding thinning or breaking of the same, which tends to occur during the initial part of the printing operation.
2. Description of Prior Art:
Pen type plotting apparatus are widely used in data processing devices and the like for recording data such as characters, figures and diagram.
A conventional pen type plotting apparatus will now be described with reference to FIGS. 1, 2 and 3. As shown in FIG. 1, a host computer 1 delivers printing data in the form of recording control commands to a pen type plotting apparatus 2. Within the pen type plotting apparatus 2, a recording control portion 3 generates, for instance, character patterns based on the printing data and finds out vector or stroke data required for forming the character patterns. The recording control portion 3 then applies the vector data to an X-Y recording mechanism 4 as analog control signals for controlling X and Y coordinates, simultaneous with a pen driving signal. Upon reception of the analog control signal and the pen driving signal delivered from the record control portion 3, the X-Y recording mechanism 4 operates a motor and an electromagnet included therein for recording desired character patterns on a recording paper 5.
FIG. 2 illustrates a practical construction of the pen type X-Y recording mechanism 4, wherein numeral 5 designates the recording paper, numeral 6 designates a carriage motor, 7 a carriage, 8 a ball pen, 9 a paper feed motor, 10 a rubber roller, and numeral 11 designates the electromagnet. Under the control of the X coordinate control signal, the carriage motor 6 is driven to control the X coordinate position of the carriage 7. On the other hand, the Y coordinate control signal controls the paper feed motor 9 so as to rotate the rubber roller 10 and to control Y-coordinate position of the recording paper 5 relative to the carriage 7. The electromagnet 11 is excited by the pen driving signal. Upon excitation the electromagnet 11 causes the ball pen 8 secured to the carriage 7 to project toward the recording paper 5, thereby setting the ball pen in a recordable condition.
FIG. 3 is an explanatory diagram for a record control operation in the pen type plotting apparatus of the above described construction. As an example, the diagram illustrates the locus of the tip of the ball pen 8 in a case where characters A, B and C are recorded. In the drawing, numeral 12 designates the starting point for recording the character A while numeral 13 designates the terminating point. Numerous arrow marks indicate the moving directions of the tip of the ball pen 8. For each of the terminating points of the linear strokes in the patterns, the recording control portion 3 in FIG. 1 determines X-Y coordinate values representing an objective position in a digital manner, D/A converts the coordinate values, and applies the converted results through a servo amplifier to the carriage motor 6 and the paper feeding motor 9.
In the above described conventional pen type plotting apparatus, however, a problem tends to be encountered when the apparatus has not been used for a considerable length of time, in that the ink in the tip portion of the ball pen is solidified and hardly delivered during an initial part of the recording operation, thus causing thinning or breaking of recorded characters and deteriorating the quality of the recorded results. For obviating the above described difficulty, some of the conventional apparatus have included means for effecting exercise writing of, for instance, a rectangular pattern at a corner of the recording paper automatically at the time of initiation of the recording operation. Such a procedure is found to be disadvantageous because a useless recording is effected on the recording paper.